Negatives: Plus and Minus, Basic

Objective

Know how to add and subtract small numbers

Example

2 - (-3) =

Answer: 5

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Explanation

There are two parts to adding and subtracting with negative numbers

1.) If you have two signs next to each other, replace it with one

+ and + become +

2 + (+3) = 2 + 3

+ and - become -

2 + (-3) = 2 - 3

- and + become -

2 - (+3) = 2 - 3

- and - become +

2 - (-3) = 2 + 3

2.) Negatives cancel out positives. Count what's left over

-2 + 3

@ @ (2 negatives)

@ @ @ (3 positives)

@ @ (cancel out)

@ @ @

@ (1 positive left over)

Answer: 1

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2 - 3

@ @ (2 positives)

@ @ @ (3 negatives)

@ @ (cancel out)

@ @ @

@ (1 negative left over)

Answer: -1

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-2 - 3

@ @ (2 negatives)

@ @ @ (3 negatives)

@ @ @ @ @ (5 negatives)

Answer: -5

To watch a Khan Academy Video, click here.

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Examples

Example 1

-5 - (-9)

-5 + 9

@ @ @ @ @ (5 negatives)

@ @ @ @ @ @ @ @ @ (9 positives)

@ @ @ @ @ (cancel out)

@ @ @ @ @ @ @ @ @

@ @ @ @ (4 positives left over)

Answer: 4

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Example 2

8 + (-3)

8 - 3

@ @ @ @ @ @ @ @ (8 positives)

@ @ @ (3 negatives)

@ @ @ @ @ @ @ @ (cancel out)

@ @ @

@ @ @ @ @ (5 positives left over)

Answer: 5

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Example 3

-4 + (-2)

-4 - 2

@ @ @ @ (4 negatives)

@ @ (2 negatives)

@ @ @ @ @ @ (6 negatives)

Answer: -6

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